Concrete vibrators



Nov. 20, 1956 Filed April 8, 1955 B. B. DE-ARDEN CONCRETE VIBRATORS 3Sheets-Sheet 1 1956 B. B. DEARDEN 2,771,279

CONCRETE VIBRATORS Filed April 8, 1955 3 Sheets-Sheet 2 FIG. 5.

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CONCRETE VIBRATORS Filed April 8, 1955 3 Sheets-Sheet 3 [madmlay I mAimqlx flaw iinite States Patent CONCRETE VIBRATORS Brian BurtonDear-den, Bramhall, England, assignor to C. H. Johnson (Machinery)Limited, Stockport, England, a British company Application April 8,1955, Serial No. 500,177

Claims. (Cl. 259-1) This invention relates to concrete vibrators of thetype known in the trade as the internal type. These machines usuallycomprise a power unit, which may be either an internal combustion engineor of the compressed air, hydraulic or electrically operated type, and avibrating unit, the latter usually comprising a rotatable out-of-balanceshaft or weight enclosed in a suitable housing, and adapted to beimmersed in a concrete mix to cause it to flow and settle by thebreaking down of internal friction in the mix, thereby causing the mixto become more dense and enabling dryer and stiffer concrete mixes to beplaced in forms, moulds and the like.

The internal type concrete vibrators are constructed in various forms,the vibrating unit being in driving connection with the power uniteither through a stiti or flexible drive shaft, or the power unit may belocated within the vibrating unit housing. Whatever the construction,the present invention is applicable to any of the above-mentionedalternatives.

A desirable feature of internal vibrating units is that they shouldvibrate with a large amplitude during the initial phases of settlementof the concrete mix, due to Wider spacing of the ingredients, but (a) asthe concrete mix settles and becomes more dense the ingredients becomemore closely pushed together, and (b) such increase in density creates alarger resistance to the vibrator thereby causing an increase in powerconsumption. Consequently the two factors (a) and (b) make it desirablefor the amplitude of the vibrator to be progressively reduced ascompaction of the concrete proceeds.

However, a still further point (0) of a practical nature arises, in thata high frequency unit operating at say 10,000 cycles per minute, or evenmore, with a large amplitude, causes severe splashing just as thevibrating unit is inserted in and removed from the concrete mix, causinginconvenience to the operator.

One object of the present invention is to provide a vibrating unit foran internal concrete vibrator wherein two rotatable out-of-balanceelements are mounted preferably co-axially so as to be angularlyadjustable relative to each other and having means for effecting suchadjustment of the elements whereby the amplitude of vibration generatedas the elements rotate can be varied.

A further object of the invention is to provide a vibrating unit whereinthe out-of-balance elements are interconnected by flexible means throughwhich the drive imparted to one element is passed on to the other, saidflexible means allowing relative angular movement to take placeautomatically as the torque to the said one element is varied.

According to a still further object of the invention, the twoout-of-balance elements are mounted co-axially and annularly arrangedand rotate at diflerent radii, the driving torque from the power unitbeing imparted to the inner element and the latter being in drivingconnection with the outer element by means of a torsional spring whoseresilience allows the elements 'automatical ly to adjust themselvesangularly relatively to each other to vary the amplitude of vibrationgenerated proportional to the variation of the driving torque and powerconsumption of the vibrator unit.

A still further object is to provide a vibrating unit wherein thetorsional spring and out-of-balance weights may be so constructed andarranged that the amplitude of vibration is initially quite small,gradually building up to a maximum, and then gradually decreasing tocomply in succession with conditions (0), (a) and (b) previouslyoutlined, the variations in the amplitude of vibration being variedaccording to the torque applied.

In the accompanying drawings is illustrated one embodiment of theinvention wherein the vibrating unit gives maximum vibration whenrunning under light load and gradually decreasing to aminimum ascompacting progresses, and in said drawing:

Fig. 1 is a longitudinal sectional elevation of the unit;

Fig. 2 is a cross section on the line 22, Fig. 1;

Fig. 3 is a cross section on the line 33, Fig. 1;

Fig. 4 is a perspective view of the two out-of-balance elements when ina state of rest and over-lying each other;

Figs. 5, 6 and 7 are detail sectional views showing the relativedispositions of the out-of-balance elements when the vibrations impartedby the unit have respectively a maximum, intermediate and minimum value.

Fig. 8 is a side elevation of a power unit comprising an internalcombustion engine; whilst Fig. 9 is an end View of Fig. 8 with thevibrator unit in driving engagement therewith.

In the example illustrated, the vibrating unit, which is constructed tocomply with conditions (a) and (b) outlined above, comprises an outerstationary casing 10 connected in usual manner to the outer casing 11 ofa flexible driving shaft (not shown) driven by an internal combustionengine. Within the vibrating unit casing and adjacent the end of theflexible drivingshaft is an antifriction bearing 12 in which isjournalled the trunnionlike end 13 of an inner out-of-balance element inthe form of an unbalanced rotor or shaft 14. Each end of the innerelement has concentric cylindrical portions 15, 16 on which isjournalled an outer out-of-balance element 17. As illustrated in Fig. 4,the element 17 comprises a sleeve-like member having a portion of itscurved surface cut away at 17 to render same out-of-balance relative toits mounting on and co-axially with the rotor 14. Although the outerelement 17 is shown as mounted on the inner element through theintermediary of bushes 18, 18 of anti-friction metal, the bushes may bereplaced by a ball or roller bearing. The end of the inner element 14remote from the flexible driving shaft is provided with a trunnion 14journalled in an anti-friction bearing 19 located in the casing 10. Theouter element is connected to the trunnion 13 of the inner element by atorsion spring 20 which provides a flexible driving connection betweenthe two elements, said spring being housed in a masking sleeve 20 andembracing the trunnion, the latter having a reduced portion 13 by whichit is connected to the flexible driving shaft (not shown). Mechanicalstops 20', 21 are mounted respectively on the inner and outerout-of-balance elements, such stops being apart and limiting therelative angular movement between said ele ments.

During assembly of the two out-of-balance elements 14, 17 they are soarranged and the stiffness of the spring so selected that when at restor running under light load, the torsion spring will lcause the outerelement 17 to over lie the inner element 14 (see Fig. 5) sothat thetotal unbalanced mass isat amaximum and therefore the amplitude ofvibration generated will al'so be at maximum value. The spring will.therefore ensure that the two elements remain in their initial positionimparting maximum vibration to the concrete mix during the early stagesof compaction of the concrete mix, but as compacting progresses and thedriving torque increases, the inherent resistance of the spring will beovercome and the inner element will take an angular lead over the outerelement (see Fig. 6) which lead will gradually increase to a maximum, asillustrated in Fig. 7. As the out-of-balance elements now tend tobalance each other, the amplitude of vibration will gradually decrease,thus keeping the power consumption of the vibrator fairly constantthroughout the compacting operation, and also satisfying the conditionsof (a) and (b) described above.

The stop means 20, 21 are embodied in the construction to prevent thelead between the two elements becoming greater than predetermined forefiicient operation.

As illustrated in Figs. 8 and 9, the power unit may comprise an internalcombustion .engine 22, which by means of a V-belt 23 drives acountershaft 24, the gear ratio being so proportioned as to give amaximum shaft speed of approximately 10,000 R. P. M. The drive from thecountershaft 24 to the vibrating unit 25 is by means of a flexible shaft26.

In an alternative construction (not illustrated), in order to complywith condition in addition to (a) and (b), the out-of-balance elementsare so arranged that when at rest one element has a lead over the other,and in addition a torsion spring is selected having two rates ofloading.

In this latter arrangement, the initial amplitude of vibration is small,gradually building up to maximum as the elements approach a point wherethey coincide, and gradually decreasing as the elements again moveangularly relative to each other as the mix becomes more compact and thetorque increases. The torsional spring would, during the first 180 ofrelative movement between the two out-of-balance elements, give only avery light resistance, which would increase during the second 180 ofrelative movement. Thus, when running light or in air, the vibratingunit would have a small amplitude, but the application of a small loadwould cause the inner rotor to advance in relation to the outer one, sothat on first immersing in the uncompacted concrete mix, the amplitudewould increase rapidly to its maximum, and thereafter progressivelydecrease as previously described.

Similarly, on removing the vibrating unit from the concrete aftercompaction, vibration at the point of reioval would be reduced andsplashing avoided.

In a further modification, instead of using a single torsion springhaving two rates of loading, two separate torsion springs may be usedeach having different rates of loading. In such case, in order that thefirst part of the movement raises the amplitude of vibration fromminimum to maximum on insertion of the vibrating unit into the concretemix, a spring of lighter loading is arranged to operate during suchmovement. As the concrete is compacted and the amplitude must bereduced, at stiifer torsion spring comes into operation. The two springswould be so selected and arranged, that minimum amplitude is reached atthe point of highest power consumption, whilst the increase from minimumto maximum amplitude only requires a small increment of powerconsumption.

What I claim is:

1. A vibrating unit for an internal concrete vibrator comprising acasing in which two out-of-balance elements are mounted co-axially andannularly arranged so that they rotate concentrically one within theother, means for imparting rotary motion to the inner element, and atorsional spring interconnecting said elements and providing a resilientdriving connection between said elements automatically to allow them toadjust themselves angularly relative to each other to vary the amplitudeof vibration generated, the outer out-of-balance element beingjournalled on the inner out-of-balance element.

2. A vibrating unit for an internal concrete vibrator, comprising acasing in which is journalled an inner outof-balance rotor elementhaving concentric portions at each end thereof, means for impartingrotary motion to said rotor element, an outer sleeve-like out-of-balanceelement surrounding said inner element and journalled on the concentricportions thereof, said sleeve-like member having a portion of its curvedsurface cut away to render it out-of-balance relative to its mounting,and a torsional spring interconnecting said elements and providing aresilient driving connection therebetween to allow them automatically toadjust themselves angularly relatively to each other to vary theamplitude of vibration generated.

3. A vibrating unit according to claim 2, wherein the torsional springis located on the inner element with one end attached to the innerelement and the other end engaging the outer element, said elementshaving complementary abutments to limit their relative angular movement.

4. A vibrating unit for an internal concrete vibrator comprising acasing in which out-of-balance inner and outer elements are mountedcoaxially and annularly arranged so that they rotate concentrically onewithin the other, means for imparting rotary motion to the innerelement, and a torsional spring interconnecting said elements andproviding a resilient driving connection between said elements toautomatically allow them to adjust themselves angularly relative to eachother to vary the amplitude of vibration generated, said outerout-of-balance element being journalled on the inner out-of-balanceelement.

5. A vibrating unit for internal concrete vibrator co1n prising a casingin which out-of-balance elements are rotatably mounted relativelyco-axially so as to be angularly adjustable relative to each other,means for imparting rotary motion to one of said elements, and flexiblemeans interconnecting said out-of-balance elements through which thedrive imparted to the driven element is conveyed to the other element,said flexible means allowing relative angular movement between theelements to take place automatically to vary the amplitude of vibrationgenerated as torque imparted to the driven element is varied.

6. A vibrating unit for an internal concrete vibrator comprising acasing in which two rotatable out-of-halance elements mounted relativelyco-axially are annularly arranged so that they rotate concentrically onewithin the other, means for imparting rotary motion to one of saidelements, and a torsional springinterconnecting said elements by whichthe drive imparted to the driven element is conveyed to the otherelement, said torsional spring allowing said elements automatically toadjust themselves angularly relative to one another to vary theamplitude of vibration generated as torque imparted to the drivenelement is varied.

7. A vibrating unit for an internal concrete vibrator comprising acasing in which is rotatably mounted an inner out-of-balance elementhaving an outer out-of-balance elementjournalled thereon, means forimparting rotary motion to the inner element, and flexible meansinterconnecting said elements and providing a resilient drivingconnection therebetween to allow them automatically to adjust themselvesangularly relative to each other to vary the amplitude of vibrationgenerated.

8. A vibrating unit for an internal concrete vibrator comprising acasing in which is rotatably mounted an inner out-of-balance elementhaving an outer out-of-balance element journalled thereon so that saidelements rotate concentrically one Within the other, means for impartingrotary motion to the inner element, a torsion spring interconnectingsaid elements and providing a driving connection between said elementsto allow them automatically to adjust themselves angularly relative toeach other to vary the amplitude of vibration generated as torqueimparted to the driven element is varied.

9. A vibrating unit for an internal concrete vibrator comprising, anelongated hollow casing, an elongated inner out-of-balance element insaid casing having opposite ends rotatably mounted in said casing, meansfor imparting rotary motion to said inner element, an elongated outerout-of-balance element having opposite ends thereof journalled onopposite end portions of said inner element for rotary motion thereofrelative to said inner element, and a torsional spring interconnectingcorresponding end portions of said elements providing a resilientdriving connection therebetween to automatically allow them to adjustthemselves angularly relative to each other to vary the amplitude of thevibration generated thereby.

10. A vibrating unit for an internal concrete vibrator comprising, anelongated hollow casing, an elongated inner out-of-balance element insaid casing having opposite ends rotatably mounted in said casing, meansfor imparting rotary motion to said inner element, an elongated outerout-of-balance element having opposite ends thereof journalled onopposite end portions of said inner element for rotary motion thereofrelative to said inner element, and a torsional spring interconnectingcorresponding end portions of said elements providing a resilientdriving connection therebetween to automatically allow them to adjustthemselves angularly relative to each other to vary the amplitude of thevibration generated thereby, and engageable stops carried by saidelements to limit relative rotative movements thereof.

References Cited in the file of this patent UNITED STATES PATENTS2,677,967 Galbraith May 11, 1954 FOREIGN PATENTS 115,501 Australia July7, 1942

